I used "say 1" as an example but nothing I've tried did work after the "run" word.

1. Type this command, no space after the final 1
   /execute unless entity @s[x=-1,z=-1,dx=0,dz=0] positioned -1201 100 -1228 positioned over ocean_floor run say 1
2. If you are NOT on coords x=-1 and z=-1, a syntax error is shown when submitting the command.
   That is not expected, that should say "1".
3. If you are on coords x=-1 and z=-1, nothing happens, as expected.

I've tried some things and it seems to only happen when the coordinates in the "positioned" part are not loaded.

Even if you believe the correct behaviour should be an error message saying "position is not loaded", it is still not the great one.

Have a nice day